197 Attention and disattention (hypnotic analgesia) to painful somatosensory tens stimuli differentially affects brain dynamics: A functional magnetic resonance imaging study

Abstract

EEG correlates of self-generated happy and sad emotions during counterbalanced conditions of waking and hypnosis were investigated in 16 low (‘lows’) and 15 highly (‘highs’) hypnotizable men, as assessed by the Harvard Group Scale of Hypnotic Susceptibility and the Stanford Hypnotic Susceptibility Scale, Form C. Using log mean spectral magnitude, 11 frequency bands (3.5–42 Hz) were evaluated at frontal (F3, F4), central (C3, C4), and parietal (P3, P4) regions. As anticipated, only parietal hemispheric differences in low alpha activity (7.5–9.45 Hz) differentiated between emotions, whereas mid and high alpha activity (9.5–13.45 Hz) did not. There was significantly less low alpha activity in right parietal (P4) in sad than happy emotions, supportive of prior research showing relatively greater right hemispheric involvement in negative than positive emotions. Yet, overall there was more low alpha activity in the left parietal (P3) region. During sadness only in waking, low beta (13.5–15.45 Hz) activity was greater in the right than left frontal region, greater in the left than right central region, and similar in both hemispheres in the parietal region. As anticipated, in comparison to lows, highs showed significantly greater hemispheric asymmetries (right greater than left) in the parietal region in high theta (5.5–7.45 Hz), high alpha (11.5–13.45 Hz), and beta activity between 16.5 and 25 Hz — all frequency bands that are associated with sustained attentional processing. Results support prior research (for reviews, see Crawford, 1994a; Crawford and Gruzelier, 1992) that highs have greater sustained attentional abilities than do lows, which is reflected in different regional brain dynamics. Future EEG research needs to address narrower EEG frequency bands, as well as consider the moderating effects of hypnotic susceptibility level in observed hemispheric asymmetries.